It is known that a double-glazing unit is constituted by two or more substantially flat glass panes, which are arranged substantially parallel to each other and are mutually spaced; the sheets of each pair of consecutive panes are mutually coupled by interposing a spacer profile, which is distributed along their entire perimeter.
In general, a double-glazing unit can be constituted by a plurality of glass panes, which are coupled in pairs by interposing a respective spacer profile; merely by way of example, double-glazing units are known which are constituted by two glass panes which are mutually coupled by interposing a spacer profile, or by three glass panes, which are coupled in pairs by interposing a respective spacer profile.
In order to better understand the configuration of a glass pane, not so much in its separate use, but rather in its use in combination with other components, including in particular the spacer profile for forming the double-glazing unit, some concepts which relate both to the intermediate products, i.e., to the glass panes and the spacer profiles, and to the finished product, i.e., the double-glazing unit, are summarized hereafter. The subsequent use of the double-glazing unit as a component of a door or window is known to the person skilled in the art and therefore is not discussed here in detail.
With reference to FIG. 1, the double-glazing unit 3 is constituted by the coupling of two or more substantially flat glass panes 2, which are mutually parallel and spaced; the two panes 2 of each pair of consecutive sheets are mutually separated by interposing a respective spacer profile, which can be constituted either by a tape 1 made of flexible material or, as an alternative, by a frame 1′, both of which are described in greater detail hereinafter.
FIG. 1 illustrates five possible sectional views of configurations of the double-glazing unit 3: 1A, 1B, 1C, 1D and 1E; these configurations differ from each other in the composition of the double-glazing unit 3, in the type of spacer profile and in the configuration and relative arrangement of the glass panes 2. In particular, in configurations 1A-1C, the spacer profile is constituted by a frame 1′, while in configurations 1D and 1E said profile is constituted by a tape 1.
The chamber 4 delimited by each pair of glass panes 2 and by the respective spacer profile may contain air or can be filled advantageously with a gas or mixture of gases injected therein, giving the double-glazing unit 3 particular insulation properties, for example thermally-insulating and/or soundproofing properties. The coupling between each pair of glass panes 2 and the respective spacer profile is achieved by means of two seals: a first seal 5, which is intended to provide the initial coupling of the glass panes 2 and of the spacer profile and the hermetic closure of the chamber 4 formed between them, and a second seal 6, which is intended to consolidate the coupling between the two glass panes 2 and the respective spacer profile and to give mechanical strength to the coupling formed between them.
The first seal 5 affects the lateral surfaces of the spacer profile in contact with the two glass panes 2 and the corresponding portions of the faces of the glass panes 2 which face each other.
The second seal 6 affects the compartment formed by the face of the spacer profile that is directed toward the outside of the chamber 4 and by the portions of the faces of the glass panes 2 which face each other and protrude from the outer face of the spacer profile up to the perimetric edge of said glass panes 2.
The glass panes 2 used to compose the double-glazing unit 3 can have a different configuration depending on their different use, for example depending on the fact that the glass pane 2 is used for the side of the double-glazing unit 3 that is directed toward the outside of the building or of the space closed by the corresponding door or window or toward its inside; in FIG. 1, the inside and the outside of the space enclosed by the double-glazing unit 3 are represented schematically by a sun and by a radiator. The glass pane 2 used for the outer side can be for example of the normal or reflective type, in order to limit the heat input in summer months, or can be of the laminated/bulletproof type, with an intrusion-resistant and/or vandalism-resistant function, or of the laminated/tempered type, with a safety function, or also of a combined type, for example reflective and laminated. The glass pane 2 used for the internal side can instead be of the normal or low-emissivity type, in order to limit the loss of heat in winter months, or can be of the laminated/tempered type with safety functions, or of a combined type, for example of the low-emissivity and laminated type.
As mentioned, the spacer profile can be constituted by a substantially rigid frame 1′, which is made for example of aluminum, steel or plastics, is internally hollow, and has small perforations in the face directed toward the inside of the chamber 4 of the double-glazing unit 3 (FIG. 1, configurations 1A-1C). The cavity 7 inside the frame 1′ is generally filled with hygroscopic material, which is not shown. The frame 1′ is an intermediate product used in the production line of the double-glazing unit; it is preformed with shapes and dimensions which correspond to those of the glass panes 2 with which it is to be coupled. If the spacer profile is constituted by a frame 1′, the first seal 5 is constituted by a thermoplastic sealant, for example a butyl sealant, which is spread over its lateral surfaces before it is applied to the glass panes 2, while the second seal 6 is constituted by a sealant, for example of the polysulfide, polyurethane or silicone type. The application of the frame 1′ to the glass panes 2 has drawbacks: in particular, the sealant of the first seal 5 tends to creep until the sealant of the second seal 6 has catalyzed completely.
As an alternative, the spacer profile can be constituted by a tape 1 made of expanded synthetic material of the flexible type, such as, merely by way of example, silicone or EPDM, which incorporates the hygroscopic material within its mass. The tape 1, a portion of which is shown in FIG. 2, has a substantially rectangular cross-section and can have different dimensions; the two opposite lateral surfaces of the tape 1, which are designed to make contact with the faces of the two glass panes 2 between which it is interposed, are coated with an adhesive 8, for example of the acrylic type, and are covered temporarily by a respective protective film 1a and 1b, which is removed when the tape 1 is applied to the glass panes 2. If the spacer profile is constituted by the tape 1, the first seal 5 is provided by the adhesive 8 itself, while the second seal 6 is constituted by a sealant, for example of the butyl type. The tape 1 is an intermediate product, which is supplied wound on spools from which it is gradually unwound in order to be applied to the glass panes 2 along a double-glazing unit production line.
In recent years, the use of the tape 1 as a spacer profile in replacement of the conventional frame 1′ has become particularly widespread; said tape has some advantages with respect to said frame: it has a lower heat transmission coefficient than the frame 1′, it adheres practically immediately and stably to the glass panes 2, since the adhesive 8 is not subject to the creep which is typical of thermoplastic sealants used for frames 1′, and it is versatile and flexible in use. It in fact allows to follow the perimeter of glass panes of any shape and size, being “shaped/contoured” simultaneously with its application thereto and without requiring, differently from the frame 1′, to be preformed and contoured with definite shapes and dimensions which match those of the glass panes 2 to which it is to be applied.
From what has been described it is evident that a double-glazing unit production line provides a plurality of successive treatments, including in particular the application of the spacer profile, each treatment being performed by a respective automatic or semiautomatic machine in a station of the line that is dedicated thereto.
Merely by way of non-limiting example, the processes which are possible but not all always necessary and are provided along a double-glazing unit production line are the following:                removing, on the peripheral face of the glass panes, of any coatings, in order to maintain over time the adhesive bonding of the first and second seals;        beveling the sharp edges of the glass panes, both to eliminate defects arising from the cut and for safety reasons, in order to reduce the risk of injury in the handling of the individual panes and of the double-glazing unit;        washing the individual panes, alternating an inside pane and an outside pane, the internal or external orientation being the one defined earlier;        applying the spacer profile, constituted either by a rigid frame, which is preformed in the machine which is external to the double-glazing unit production line, or by a tape made of a flexible material wound on a spool. In the first case, a thermoplastic sealant is spread beforehand on the opposite lateral surfaces of the preformed frame; in the second case, the tape is unwound from the spool and, after removing the protective films from its opposite lateral surfaces, it is shaped so as to constitute a closed profile along the entire perimeter of the glass pane simultaneously with its application thereon;        coupling and pressing the assembly formed by the glass panes and the spacer profile or spacer profiles;        filling the resulting chamber or chambers with gas;        second sealing.        
With particular reference to the application of the spacer profile constituted by a tape made of flexible material, automatic machines for manufacturing it are known and are for example the subject of US2003/0178127 and EP-A-0770755.
US2003/0178127 discloses an automatic machine for applying an elastoplastic spacer tape, which comprises substantially a surface for supporting a glass pane which lies slightly inclined with respect to the vertical, a horizontal conveyor located proximate to the lower edge of the supporting surface, and a post which is arranged on a plane which is substantially parallel to the supporting surface and along which an application head is supported movably, said head being able to rotate about an axis which is substantially perpendicular to the supporting surface. The application head rigidly supports means for feeding the tape to be applied, which are provided with a section for compensating the length of tape that is fed, said means being suitable to avoid the onset of abnormal slackening or tensions of said tape. The fed tape is unwound from a motorized storage spool, which is located remotely with respect to the application head, i.e., the spool is arranged in a feeder station located proximate to the machine. The portion of tape unwound from the spool which runs from the feeder station to the feeder means rigidly coupled to the application head can be guided along a predefined path, which is flexible and whose length can vary depending on the movements of the application head.
However, this machine has drawbacks, including the fact that despite the presence of the compensation section rigidly coupled to the application head, the portion of tape that runs along the path from the feeder station to the application head is subjected to traction and/or shearing tensions, or to abnormal slackenings, which cause application defects, such as shrinkages or undulations, which due to the elastoplasticity of the material that constitutes the tape may also become apparent over time. The length of the path that leads from the feeder station to the application head is in fact not only considerable but also variable over time due to the translational and rotary motions of the application head, and this prevents precision control of the state of the stresses to which the tape is subjected along said path.
Another drawback is that the feeder station and the guiding path that leads the tape from the feeder station to the application head have significant dimensions and installation, management and maintenance costs.
Another drawback is constituted by the fact that the operations for replacing the spool of tape, both when the preceding spool is depleted and when it is necessary to use a different type of tape, are laborious and require long execution times, which slow down production; it is in fact necessary to insert the portion of tape that runs from the feeder station to the application head along the corresponding guiding path.
EP-A-0770755 discloses an automatic machine for applying a tape made of flexible material, particularly a thermoplastic tape reinforced with a metal core, which is constituted substantially by a robotized manipulation arm which works according to a system of Cartesian coordinates.
The manipulation arm has an end which is associated with a supporting base and an opposite end with which a tape application head is associated, said head rigidly supporting a cradle for supporting a motorized tape feeder spool. In particular, the manipulation arm is of the type with at least six axes and can move the application head with a translational motion and/or a rotary motion with respect to axes which are parallel and perpendicular to the plane of arrangement of the glass pane, so as to be able to follow its perimeter continuously. The arm works on a glass pane which is arranged on a substantially horizontal supporting surface; the arm moves the application head with respect to the glass pane, which is kept stationary, so as to apply the tape along its entire perimeter. To form corners or follow arc-like portions of the perimeter of the glass pane, the arm turns through a corresponding angle the application head, the motorized spool rotating rigidly with the head.
This machine also, however, has drawbacks, including the fact that it provides inaccurate, defective and low-quality comers and arc-like profiles, due to the inertial effects and oscillations caused by the rotation of the spool and of the corresponding motor rigidly with the application head.
In order to obviate this drawback and improve the quality of the comers and arc-like profiles, it is possible to oversize the manipulation arm, but this entails both a disadvantageous increase in production, installation and management costs and a disadvantageous increase in space occupation and maneuvering spaces.
As an alternative, it is possible to slow the movements, particularly the rotary movements, of the application head, but this entails a disadvantageous slowing of production.